What size Impact Driver do I need? Beginners to Professional Guide!

What size Impact Driver do I need? Beginners to Professional Guide!

The most commonly asked question when choosing an impact driver is, “What size impact driver do I need?” That depends on the job you are doing. If the job requires a lot of driving time, then a larger impact driver will work better. A smaller one will work faster if the driving time is less.

What is an Impact Driver? How does It work?

Impact drivers can be used for both fastening and loosening screws: when the trigger is pulled, an impact mechanism forces a hammering head to repeatedly strike the screw and drive it deeper into its target. In comparison to standard drill bits, impact drivers can make driving screws easier.

A standard drill bit requires you to hold the bit steady while pulling the trigger and applying pressure on the drill.

An impact driver allows you to hold the bit in place with one hand and pull the trigger with your other hand. This makes it much easier for users with physical impairments or exhaustion to drive screws into a variety of surfaces.
Anyone who has ever tried putting together IKEA furniture can tell you how much of a pain in the you-know-what it is without power tools.

How many Sizes of Impact Drivers are there?

There are three main sizes of impacts:

  • 1/41/450mm: 1/4 hex shank- – 6.35mm square head
  • 3/81/450mm: 3/8 hex shank – – 9.53 mm square head
  • 1/21/450mm: 1/2 hex shank – – 12.7mm square head

The smallest is 1/4″ Hex Shank which is 1.5″ in length while the largest is a 1/2″ Hex Shank which is 2.37″ long.

 ¼ Impact Driver

This is the smallest of the 3 impact drivers that we will be looking at today. It features a 1/4″ hex shank and can be used on all standard-size screwdriver bits. This makes it ideal for basic DIY jobs around your home, such as hanging pictures or changing doorknobs.

⅜ Impact Driver

This is the most popular “mid-range” size of an impact driver and is certainly the one I would recommend most out of the two choices above. It has a 3/8″ hex shank so it can be used with all standard-sized screwdriver bits and drill bits up to that size as well.

This is a much more versatile size than the 1/4″ size because it can be used on larger projects such as building decks, sheds, and even installing cabinets!

½” Impact Driver

They are extremely powerful! It has ½” hex shank.

What is the most common Impact driver Size?

In contrast to drills, impact drivers do not come with a three-jaw self-centering chuck. The chuck is instead a quick-release hexagonal one that accepts bits with hexagonal shanks.

Despite the fact that many impact drivers use a 3/8-inch fitting, it is more common to use a 1/4-inch fitting.

What size Impact driver do I need for Lug nuts?

lug nuts impact driver
lug nuts impact driver

The next question is, “What size impact driver is suitable for lug nuts?” The answer is simple; any size impact driver will work on lug nuts as long as it’s not over-torqued.

If there is too much pressure, the head of the lug nut can become stripped and no longer round-shaped. Sometimes even if the lug nut is still round, it can become distorted enough to make it difficult to remove with hand tools. The socket that fits in an impact driver has a 1/4″ hex drive on it and can be used for lug nuts.

What size is an impact driver chuck?

Choosing an impact driver will require you to understand the term ‘chuck size’. The chuck size is determined by the maximum diameter of the shank.

Larger chucks are able to handle shanks with larger diameters. Impact drivers have hexagonal chucks of 6.35mm (1/4″). They can therefore use hexagonal bits only up to 6.35mm in diameter.

Selecting a chuck requires you to measure the shank diameter of the bits you want to use, and select the right size chuck based on that measurement.

Read more: Drywall Screwdrivers vs Drill vs Impact Driver

What is the best impact driver for home use?

An impact driver offers many advantages over an ordinary drill. It combines the speed of a drill with the ability to drive in long screws using a spinning motion rather than a repetitive motion. A powerful unit can even drive in long large bolts and concrete screws without any problem at all.

The best impact driver for home use is the DeWalt DCF787. It is a cordless impact driver with ¼ inch hex chuck. Moreover, it is highly compact and lightweight.

Its grip is also very comfortable and it is easy to use. Furthermore, it comprises a brushless motor that delivers versatile power and speed. You can work with it on a deck, yard, and in tight spaces. Thus, it’s the best choice for home use.

They’re also convenient and easy to use, unlike drills, and don’t produce dust or heat. The move toward energy-efficient solar panels and wind turbines is encouraging the use of impact drivers.

Which Impact driver has the most Torque?

A torque is the ability of an impact driver to twist. It determines its performance. High torque = high twisting power. Measured in inch-pounds (often written as in-lbs.)

For example, an impact driver with a torque of 800 in-lbs. at home or in a workshop is plenty of torque to drive screws. Large screws, such as those used in decks and house frames, require the impact driver with 1,500 lbs. of torque. Materials determine torque requirements. Softwood screws need less torque than hardwood screws.

DeWalt DCF887 has the most torque. It offers a torque of about 1825 IN-LBS at maximum setting. The reason behind this high torque is the excellent brushless technology.

This technology has enabled the motor to work on high levels of torque. Thus, you can drive hard screws with it, drive lug nuts and tighten carriage bolts.


An impact driver can make all of the difference on those projects, with its ability to make driving lag bolts or hammering large screws in half the time. Impact driver sizes are highly dependent on the types of jobs you are going to do.

Thus, by getting the answer to your question, “what size impact driver do I need?” You can quickly and efficiently get your job done and they are not just for construction: if you have a project around the house that requires driving a small but stubborn screw, an impact driver is your ticket to finishing those projects faster and easier than ever.

Bahram Shahab
Bahram here! A certified Electrical Engineer who knows his way around using power tools like a professional. My journey of using these robust tools started back when I graduated. Since then, I have finished almost a dozen DIY woodworking jobs. Apart from that, I have developed this habit of jotting down my personal experience about using a specific tool. So, I write on them to help the community in the best possible way.